_Thamnophis sirtalis parietalis_ Say was described (as _Coluber parietalis_) in 1823 from a specimen obtained in what is now Washington County, Nebraska, on the west side of the Missouri River three miles upstream from the mouth of Boyer's River [Iowa], or approximately eight miles north of Omaha. Although the type locality was unequivocally stated in the original description, Nebraska was not mentioned since the state was not yet in existence. Because the mouth of Boyer's River, the landmark by means of which the type locality is defined, is in Iowa, the impression has been imparted that the type locality itself is in Iowa (Schmidt, 1953:175), and to our knowledge the type locality has never been associated with Nebraska in the literature. Like all the more western subspecies, _parietalis_ is strikingly different from typical _sirtalis_ in having conspicuous red markings. The relationship between the two was early recognized. Several of the other subspecies were originally described as distinct species. _Coluber infernalis_ Blainville, 1835; _Tropidonotus concinnus_ Hallowell, 1852; _Eutainia pickeringi_ Baird and Girard, 1853; and others now considered synonyms eventually came to be recognized as conspecific with _Thamnophis sirtalis_. Ruthven (1908:166-173) allocated all western _sirtalis_ to either _parietalis_ or _concinnus_, the latter including the populations of the northwest coast in Oregon, Washington and British Columbia. Subsequent more detailed studies by later workers with more abundant material led to the recognition of some subspecies that Ruthven thought invalid and led to the resurrection of some names that he had placed in synonomy. Van Denburgh and Slevin (1918:198) recognized _infernalis_ as the subspecies occurring over most of California and southern Oregon, differing from more northern populations in having more numerous ventrals and caudals and a paler ground color. Fitch (1941:575) revived the name _pickeringii_ for a melanistic population of western Washington and southwestern British Columbia, restricting the name _concinnus_ to a red-headed and melanistic population of northwestern Oregon, and restricting the name _infernalis_ to a pale-colored population in the coastal strip of California.